As a semiconductor device in which pixels each including a photosensor are arranged in a matrix, a CMOS image sensor is known. CMOS image sensors are provided in many portable devices such as digital cameras or cellular phones as imaging elements. In recent years, a pixel in the CMOS image sensor has been made smaller in accordance with the increase in definition of imaging and the reduction in size and power consumption of portable devices.
A color imaging data is obtained in a CMOS image sensor in such a manner that color filters are formed over photosensors, incident light is dispersed by the color filters, and then light with each color is detected by the photosensor. However, a color filter transmits light in a specific wavelength range and absorbs light having the other wavelengths, and thus the use efficiency of incident light is low. Therefore, Patent Document 1 discloses a technique in which a component for dispersing incident light is used instead of a color filter.